Hazard Mitigation Through Gas Flow Communication Between Battery Packs

ABSTRACT

A system and method for mitigating the effects of a thermal event within a non-metal-air battery pack is provided in which the hot gas and material generated during the event is directed into the metal-air cells of a metal-air battery pack. The metal-air cells provide a large thermal mass for absorbing at least a portion of the thermal energy generated during the event before it is released to the ambient environment. As a result, the risks to vehicle passengers, bystanders, first responders and property are limited.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims benefit of the filing date of U.S. ProvisionalPatent Application Ser. No. 61/372,351, filed Aug. 10, 2010, thedisclosure of which is incorporated herein by reference for any and allpurposes.

FIELD OF THE INVENTION

The present invention relates generally to batteries and, moreparticularly, to means for mitigating the effects and hazards associatedwith a battery pack thermal event.

BACKGROUND OF THE INVENTION

Batteries come in a wide variety of types, chemistries andconfigurations, each of which has its own merits and weaknesses. Amongrechargeable batteries, also referred to as secondary batteries, one ofthe primary disadvantages is their relative instability, often resultingin these cells requiring special handling during fabrication, storageand use. Additionally, some cell chemistries, for example lithium-ionsecondary cells, tend to be more prone to thermal runaway than otherprimary and secondary cell chemistries.

Thermal runaway occurs when the internal reaction rate of a batteryincreases to the point that more heat is being generated than can bewithdrawn, leading to a further increase in both reaction rate and heatgeneration. Eventually the amount of generated heat is great enough tolead to the combustion of the battery as well as materials in proximityto the battery. Thermal runaway may be initiated by a short circuitwithin the cell, improper cell use, physical abuse, manufacturingdefects, or exposure of the cell to extreme external temperatures.

During the initial stages of a thermal runaway event, the cellundergoing runaway becomes increasingly hot due to the increasedreaction rate and the inability of the system to withdraw the heat at arapid enough rate. As the temperature within the cell increases, so doesthe pressure. While the safety pressure release vent built into manycells may help to release some of the gas generated by the reaction,eventually the increased temperature in concert with the increasedinternal cell pressure will lead to the formation of perforations in thecell casing. Once the cell casing is perforated, the elevated internalcell pressure will cause additional hot gas to be directed to thislocation, further compromising the cell at this and adjoining locations.

While the increase in cell temperature during a thermal runaway event issufficient to damage materials in proximity to the event and to lead tothe propagation of the event to adjoining cells, it is not until the hotgas escapes the confines of the cell, and potentially the confines ofthe battery pack, that the risk to people and property damage issignificant. This is because while the event is confined, the gasgenerated by the event is primarily composed of carbon dioxide andhydrocarbon vapors. As a result, the autoignition temperature (AIT) ofcombustible materials in proximity to the event is relatively high.However, once this gas exits the confines of the cell/battery pack andcomes into contact with the oxygen contained in the ambient atmosphere,the AIT of these same materials will decrease significantly, potentiallyleading to their spontaneous combustion. It is at this point in theevent cycle that extensive collateral property damage is likely to occurand, more importantly, that the risks to the vehicle's passengersleaving the vehicle, or to first responders attempting to control theevent, becomes quite significant.

Accordingly, it is desirable to delay the escape of hot gas from thecell or cells undergoing thermal runaway to the ambient environment aslong as possible. Similarly, it is desirable to lower the temperature ofthe hot gas before it reaches the ambient environment, thereby furtherlowering the risks to passengers, bystanders and first responders, aswell as reducing the potential for the spontaneous combustion ofmaterials in proximity to the event. The present invention provides asystem and method for achieving these goals, thereby limiting collateraldamage and the risk to first responders and others.

SUMMARY OF THE INVENTION

The present invention provides a system and method for mitigating theeffects of a thermal event within a non-metal-air battery pack. Inaccordance with the invention, the hot gas and material generated duringthe event is directed through the metal-air cells of a metal-air batterypack, the metal-air cells providing a large thermal mass for absorbingat least a portion of the generated thermal energy before it is releasedto the ambient environment, thereby lowering the risk to vehiclepassengers, bystanders and first responders as well as limitingcollateral property damage.

In at least one embodiment of the invention, a hazard mitigation systemis disclosed that includes a power source comprised of a metal-airbattery pack that includes at least first, second and third airpassageways and a non-metal-air battery pack that includes a hot gasoutlet; means for coupling the hot gas outlet to the third airpassageway; and a first valve that controls the air flow out of thenon-metal-air battery pack and through at least a portion of theplurality of metal-air cells comprising the metal-air battery pack. Thefirst valve is configured to prevent air flow during normal power sourceoperation and permit air flow upon the occurrence of a thermal eventwithin the non-metal-air battery pack. The first valve may be configuredto switch from the second position in which air flow is prevented to thefirst position in which air flow is permitted when a preset temperatureor pressure within the non-metal-air battery pack is reached and/orexceeded. The hazard mitigation system may further comprise a systemcontroller coupled to the first valve and at least one temperaturesensor within the non-metal-air battery pack, wherein the systemcontroller switches the valve from closed to open (e.g., from a secondposition to a first position) when a temperature monitored by thetemperature sensor exceeds a preset temperature that corresponds to atleast one of the non-metal-air cells within the non-metal-air batterypack entering into thermal runaway. The hazard mitigation system mayfurther comprise a system controller coupled to the first valve and atleast one pressure sensor within the non-metal-air battery pack, whereinthe system controller switches the valve from closed to open (e.g., froma second position to a first position) when a pressure monitored by thepressure sensor exceeds a preset pressure that corresponds to at leastone of the non-metal-air cells within the non-metal-air battery packentering into thermal runaway. The hazard mitigation system may furthercomprise a second valve corresponding to the first air passageway of themetal-air battery pack, the second valve configured to close upon theoccurrence of a thermal event within the non-metal-air battery pack asevidenced, for example, by the temperature and/or pressure within thenon-metal-air battery pack exceeding a preset temperature or pressure.The hazard mitigation system may further comprise a second valvecorresponding to the first air passageway of the metal-air battery packand a system controller coupled to both the first and second valves,wherein the system controller may open the first valve and close thesecond valve when (i) a temperature monitored by a temperature sensorwithin the non-metal-air battery pack exceeds a preset temperatureand/or (ii) a pressure monitored by a pressure sensor within thenon-metal-air battery pack exceeds a preset pressure. The hazardmitigation system may further comprise a second valve corresponding tothe first air passageway of the metal-air battery pack, a third valvecorresponding to the second air passageway of the metal-air batterypack, at least a first temperature sensor within the non-metal-airbattery pack, at least a second temperature sensor within the metal-airbattery pack and a system controller coupled to the first, second, andthird valves as well as the first and second temperature sensors,wherein the system controller (i) opens the first valve and closes thesecond valve when the temperature within the non-metal-air battery packexceeds a first preset temperature, (ii) maintains the third valve in aclosed position when the temperature within the non-metal-air batterypack exceeds the first preset temperature and the temperature within themetal-air battery pack is less than a second preset temperature, and(iii) opens the third valve when the temperature within thenon-metal-air battery pack exceeds the first preset temperature and thetemperature within the metal-air battery pack exceeds the second presettemperature. The hazard mitigation system may further comprise a secondvalve corresponding to the first air passageway of the metal-air batterypack, a third valve corresponding to the second air passageway of themetal-air battery pack, at least a first pressure sensor within thenon-metal-air battery pack, at least a second pressure sensor within themetal-air battery pack and a system controller coupled to the first,second, and third valves as well as the first and second pressuresensors, wherein the system controller (i) opens the first valve andcloses the second valve when the pressure within the non-metal-airbattery pack exceeds a first preset pressure, (ii) maintains the thirdvalve in a closed position when the pressure within the non-metal-airbattery pack exceeds the first preset pressure and the pressure withinthe metal-air battery pack is less than a second preset pressure, and(iii) opens the third valve when the pressure within the non-metal-airbattery pack exceeds the first preset pressure and the pressure withinthe metal-air battery pack exceeds the second preset pressure. Thehazard mitigation system may further comprise a second valvecorresponding to the first air passageway of the metal-air battery pack,a third valve corresponding to the second air passageway of themetal-air battery pack, at least a first temperature sensor within thenon-metal-air battery pack, at least a first pressure sensor within themetal-air battery pack and a system controller coupled to the first,second, and third valves as well as the first temperature sensor and thefirst pressure sensor, wherein the system controller (i) opens the firstvalve and closes the second valve when the temperature within thenon-metal-air battery pack exceeds a preset temperature, (ii) maintainsthe third valve in a closed position when the temperature within thenon-metal-air battery pack exceeds the preset temperature and thepressure within the metal-air battery pack is less than a presetpressure, and (iii) opens the third valve when the temperature withinthe non-metal-air battery pack exceeds the preset temperature and thepressure within the metal-air battery pack exceeds the preset pressure.The hazard mitigation system may further comprise a second valvecorresponding to the first air passageway of the metal-air battery pack,a third valve corresponding to the second air passageway of themetal-air battery pack, at least a first pressure sensor within thenon-metal-air battery pack, at least a first temperature sensor withinthe metal-air battery pack and a system controller coupled to the first,second, and third valves as well as the first temperature sensor and thefirst pressure sensor, wherein the system controller (i) opens the firstvalve and closes the second valve when the pressure within thenon-metal-air battery pack exceeds a preset pressure, (ii) maintains thethird valve in a closed position when the pressure within thenon-metal-air battery pack exceeds the preset pressure and thetemperature within the metal-air battery pack is less than a presettemperature, and (iii) opens the third valve when the pressure withinthe non-metal-air battery pack exceeds the preset pressure and thetemperature within the metal-air battery pack exceeds the presettemperature. In at least one embodiment, the coupling means comprises aduct, wherein the hazard mitigation system further comprises a secondvalve corresponding to the first air passageway of the metal-air batterypack, and a third valve corresponding to the third air passageway of themetal-air battery pack, wherein during normal operation of the powersource the third valve is closed, and wherein when a thermal eventoccurs in the non-metal-air battery pack, for example as evidenced bythe temperature within the non-metal-air battery pack exceeding a presettemperature or the pressure within the non-metal-air battery packexceeding a preset pressure, the second valve is closed and the thirdvalve is opened. The hazard mitigation system may further comprise aplenum to direct the flow of air from the first and third airpassageways through the plurality of metal-air cells. The non-metal-airbattery pack may further comprise a high pressure relief valve.

In at least one other embodiment of the invention, a method ofmitigating the effects of a thermal event within a non-metal-air batterypack is disclosed, the method including the steps of coupling a hot gasoutlet corresponding to the non-metal-air battery pack to an air inletof a metal-air battery pack upon the occurrence of the thermal eventwithin the non-metal-air battery pack and directing air flow from thehot gas outlet through the air inlet and through a plurality ofmetal-air cells within the metal-air battery pack. The method mayfurther include the step of opening a valve that controls the air flowfrom the hot gas outlet when the temperature within the non-metal-airbattery pack exceeds a preset temperature that corresponds to at leastone of the non-metal-air cells entering into thermal runaway. The methodmay further include the step of opening a valve that controls the airflow from the hot gas outlet when the pressure within the non-metal-airbattery pack exceeds a preset pressure that corresponds to at least oneof the non-metal-air cells entering into thermal runaway. The method mayfurther include the step of monitoring a temperature within thenon-metal-air battery pack, comparing the monitored temperature to apreset temperature that corresponds to at least one of the non-metal-aircells entering into thermal runaway, and opening a valve that controlsthe air flow from the hot gas outlet when the monitored temperatureexceeds the preset temperature. The method may further include the stepof monitoring a pressure within the non-metal-air battery pack,comparing the monitored pressure to a preset pressure that correspondsto at least one of the non-metal-air cells entering into thermalrunaway, and opening a valve that controls the air flow from the hot gasoutlet when the monitored pressure exceeds the preset pressure. Themethod may further include the steps of opening a first valve thatcontrols the air flow from the hot gas outlet and closing a second valvethat controls air flow from a primary air source through the metal-airbattery pack inlet when the temperature within the non-metal-air batterypack exceeds a first preset temperature that corresponds to at least oneof the non-metal-air cells entering into thermal runaway, where theprimary air source is different from the hot gas outlet. The method mayfurther include the steps of closing a third valve that controls airflow out of the metal-air battery pack when the non-metal-air batterypack temperature exceeds a first temperature and opening the third valvewhen the metal-air battery pack temperature exceeds a second temperatureor when the metal-air battery pack pressure exceeds a preset pressure.The method may further include the steps of closing a third valve thatcontrols air flow out of the metal-air battery pack when thenon-metal-air battery pack pressure exceeds a first pressure and openingthe third valve when the metal-air battery pack pressure exceeds asecond pressure or when the metal-air battery pack temperature exceeds apreset temperature.

A further understanding of the nature and advantages of the presentinvention may be realized by reference to the remaining portions of thespecification and the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates the primary components of an electric vehicle thatutilizes both a metal-air battery pack and a conventional battery pack;

FIG. 2 illustrates the basic elements of a hazard mitigation system inaccordance with the invention, the figure showing operation of thebattery packs during a normal operational period;

FIG. 3 provides the same hazard mitigation system shown in FIG. 2,modified to show operation when one or more non-metal-air cells enterinto thermal runaway;

FIG. 4 provides the same hazard mitigation system shown in FIG. 2,modified to show operation as the pressure within the metal-air batterypack exceeds a preset level;

FIG. 5 provides the same hazard mitigation system shown in FIG. 2,modified to show operation of a secondary high pressure relief valve;

FIG. 6 illustrates an embodiment in which both non-metal-air cells andmetal-air cells are contained within a single battery pack;

FIG. 7 illustrates a modification of the embodiment shown in FIG. 6 inwhich a barrier separates the non-metal-air cells from the metal-aircells;

FIG. 8 illustrates an embodiment utilizing a metal-air battery pack anda conventional battery pack with a duct interposed between the twopacks;

FIG. 9 illustrates a modification of the embodiment shown in FIG. 8which allow the duct of the system shown in FIG. 8 to be minimized oreliminated;

FIG. 10 illustrates a modification of the embodiment of FIG. 6 utilizinga system controller;

FIG. 11 illustrates a modification of the embodiment of FIG. 7 utilizinga system controller;

FIG. 12 illustrates a modification of the embodiment of FIG. 8 utilizinga system controller;

FIG. 13 illustrates a modification of the embodiment of FIG. 9 utilizinga system controller; and

FIG. 14 illustrates a modification of the embodiment of FIG. 13 in whichthe system controller monitors pressure and/or temperature within themetal-air battery pack.

DESCRIPTION OF THE SPECIFIC EMBODIMENTS

In the following text, the terms “battery”, “cell”, and “battery cell”may be used interchangeably. The term “battery pack” as used hereinrefers to one or more individual batteries that are electricallyinterconnected to achieve the desired voltage and capacity for aparticular application. The individual batteries of a battery pack aretypically contained within a single piece or multi-piece housing,although it is possible to include multiple battery packs within asingle piece or multi-piece housing as described below. The term“electric vehicle” as used herein refers to an all-electric vehicle,also referred to as an EV, a plug-in hybrid vehicle, also referred to asa PHEV, or a hybrid vehicle (HEV), a hybrid vehicle utilizing multiplepropulsion sources one of which is an electric drive system. It shouldbe understood that identical element symbols used on multiple figuresrefer to the same component, or components of equal functionality.Additionally, the accompanying figures are only meant to illustrate, notlimit, the scope of the invention and should not be considered to be toscale.

Secondary cells may utilize any of a variety of different cellchemistries. As used herein, a ‘conventional’ cell or ‘conventional cellchemistry’ refers to a cell that utilizes lithium ion (e.g., lithiumiron phosphate, lithium cobalt oxide, other lithium metal oxides, etc.),lithium ion polymer, nickel metal hydride, nickel cadmium, nickelhydrogen, nickel zinc, silver zinc, or similar battery chemistry. Incontrast and as used herein, a ‘metal-air cell’ refers to a cell thatutilizes oxygen as one of the electrodes, typically passing the oxygenthrough a porous metal electrode. The exact nature of the reaction thatoccurs in a metal-air battery depends upon the metal used in the anodeand the composition of the electrolyte. Exemplary metals used in theconstruction of the anode include zinc, aluminum, magnesium, iron,lithium and vanadium. The cathode in such cells is typically fabricatedfrom a porous structure with the necessary catalytic properties for theoxygen reaction. A suitable electrolyte, such as potassium hydroxide inthe case of a zinc-air battery, provides the necessary ionicconductivity between the electrodes while a separator prevents shortcircuits between the battery electrodes.

Due to the use of oxygen as one of the reactants, metal-air cells offera number of advantages over a conventional rechargeable battery, mostnotably their high energy density and high capacity-to-volume, orcapacity-to-weight, ratio. Given these advantages, they are well suitedfor use in electric vehicles, especially in a dual source configurationin which one or more metal-air battery packs are used in conjunctionwith one or more conventional battery packs (e.g., lithium ion batterypack(s)). This configuration is illustrated in FIG. 1 which shows theprimary components of an EV 100 that utilizes both a metal-air batterypack 101 and a conventional, non-metal-air battery pack 103. Aspreviously noted, as used herein metal-air batteries refer to any cellthat utilizes oxygen as one of the electrodes and metal (e.g., zinc,aluminum, magnesium, iron, lithium, vanadium, etc.) in the constructionof the other electrode. Conventional battery pack 103 utilizesnon-metal-air cells, and preferably ones that provide high powerdensity, thus providing a combined power source that achieves an optimalcombination of energy and power. Exemplary batteries used inconventional battery pack 103 include, but are not limited to, lithiumion (e.g., lithium iron phosphate, lithium cobalt oxide, other lithiummetal oxides, etc.), lithium ion polymer, nickel metal hydride, nickelcadmium, nickel hydrogen, nickel zinc, silver zinc, etc. In a preferredapplication, battery packs 101 and 103 are coupled to one or more drivemotors 105 that provide propulsion to one or more wheels of EV 100. Acontroller 107 optimizes the vehicle's dual power source, i.e., batterypacks 101 and 103, in light of the current battery pack conditions(e.g., state-of-charge, temperature, etc.), preferred battery packcharge/discharge conditions, and the various operating conditions.Exemplary operating conditions include those placed on the system by theuser (e.g., distance, speed, acceleration, etc.), road conditions (e.g.,uphill, downhill, traffic, etc.), charging system (e.g., availablepower, available time for charging, etc.), and environmental conditions(e.g., ambient temperature, humidity, etc.).

The gas communication system disclosed herein may be used to mitigatethe effects of one or more cells within a conventional battery packundergoing thermal runaway, or undergoing a similar thermal event. FIGS.2-5 schematically illustrate the basic operation of the hazardmitigation system of the present invention. It should be understood thatthese figures, as well as those that follow, are intended to illustratethe operation of the invention, and therefore do not show other aspectsof a system utilizing the disclosed dual power source. For example,these figures do not show the power electronics, control system, anddrive train components that would be necessary to use the dual powersource in an electric vehicle, as previously illustrated in FIG. 1. Itwill be appreciated, however, that the inventors envision the use of thedual power source with the disclosed hazard mitigation system within anelectric vehicle (i.e., EV, PHEV, HEV, etc.) as well as otherapplications.

In accordance with the invention, during normal use, e.g., during normalvehicle operation, metal-air battery pack 101 and conventional batterypack 103 operate in a manner consistent with a conventional dual powersource system. As such, power may be drawn from one or both batterypacks 101 and 103, depending upon current battery pack conditions (e.g.,state-of-charge (SOC), temperature, etc.) and system needs (e.g.,vehicle needs such as speed, acceleration, road conditions, etc.). FIG.2 illustrates operation of the battery packs during this normaloperational period. As shown, preferably conventional battery pack 103(also referred to herein as the non-metal-air battery pack) is sealedfrom the ambient environment. Metal-air battery pack 101 is necessarilyopen to the ambient environment as the metal-air cells within metal-airbattery pack 101 require oxygen, for example taken from the ambientatmosphere, since oxygen is one of the reactants and therefore isnecessary in order for the cells to discharge. Battery pack 101 alsorequires a volume, such as the ambient environment or a containersystem, during the charge cycle when oxygen-rich effluent is generated.Due to the requirement for oxygen during operation, typically all of themetal-air cells within metal-air battery pack 101 are provided withequal access to the air flow. For example, in the exemplary system shownin FIG. 2, metal-air cells 201 are shown positioned in parallel relativeto air passageways 203 and 205. In this configuration, either passagewaymay be used as an inlet, leaving the other passageway to operate as anair outlet. Other approaches may be used to insure sufficient air flowto each of the metal-air cells within pack 101. For example, air may beforced through a plenum that is used to feed the entering air to each ofthe cells. It will be appreciated that the present invention is notlimited to a specific metal-air cell configuration within battery pack101, as long as the metal-air cells are provided with sufficient accessto oxygen, thus ensuring proper operation.

FIG. 3 illustrates the next stage of operation, when a cell or cellswithin the non-metal-air battery pack 103 enter into thermal runaway. Atthis stage, a valve 301 corresponding to conventional battery pack 103opens. As noted in more detail below, valve 301 may be a pressure valvethat opens when the pressure within battery pack 103 exceeds a presetpressure limit. Alternately, valve 301 may open when the temperaturewithin battery pack 103 exceeds a preset temperature. Alternately, valve301 may be under the control of a system controller that determines whento open valve 301, for example by monitoring pressure and/or temperaturewithin battery pack 103. Note that valve 301 may be a simple open/closevalve, or may open in stages, for example depending upon the pressureand/or temperature within pack 103. Once valve 301 opens, the hot gasand material generated during the non-metal-air cell(s) thermal runawayevent escapes from pack 103 and is directed into metal-air battery pack101, and through the metal-air cells 201, as illustrated. Note that asthe purpose of the invention is to mitigate hazards by delaying the hotgas generated during the event from reaching the ambient atmosphere,preferably the pathway 303 that couples the two battery packs is sealedto prevent, or at least minimize, the hot gas exiting from pack 103 fromcoming into contact with the ambient environment. Various ways ofsealing this passageway are described more fully below.

In addition to forming a pathway between the non-metal-air battery pack103 and the metal-air battery pack 101 during this stage, preferablyoutlets (e.g., passageway 205) from the metal-air battery pack areclosed. Once the pressure becomes great enough, and as illustrated inFIG. 4, valve 205 is opened. Opening valve 205 allows the hot gasescaping from conventional battery pack 103 to pass completely throughmetal-air battery pack 101. Depending upon the size of the thermalevent, as well as the thermal mass of the metal-air cells 201 withinmetal-air pack 101, potentially the temperature of the hot gas passingthrough the metal-air pack has been sufficiently lowered to eliminate,or greatly reduce, the risk of spontaneous combustion.

In a typical configuration, the hot gas and material generated duringthe thermal event will eventually clog the pores of the porous metalelectrodes of metal-air cells 301. Accordingly, in the preferredembodiments of the invention, at least one secondary high pressurerelief valve 501 is included in battery pack 103 as shown in FIG. 5. Thepreset relief pressure for valve 501 is set at a much higher value thanthat of valve 301. The purpose of valve 501 is to provide a means forrelieving the pressure within conventional battery pack 103 once the hotgas generated during the thermal event is no longer able to pass throughthe metal-air cells 301 of metal-air pack 101 and the pressure withinthe system begins to raise to an undesirable level.

As previously noted, the present invention is not limited to a specificconfiguration for battery packs 101 and 103 as long as the necessary airflow requirements of the invention can be met by the selectedconfiguration. For example, in the embodiment shown in FIG. 6, a singlebattery pack 601 is used, this battery pack including both metal-airbattery pack 101 and non-metal-air battery pack 103. Note that as usedin this configuration, battery packs 101 and 103 refer to groups ofcells and as such, the groups of cells may or may not be containedwithin enclosures that are distinct from the enclosure of battery pack601. In system 600, the groups of cells are not contained withindistinct enclosures and therefore metal-air battery pack 101, containingmetal-air cells 603, and non-metal-air battery pack 103, containingnon-metal-air cells 605, are shown in phantom. If cells 603 and 605 arenot contained within separate enclosures, the system may or may notutilize a separation barrier between the cell types. A separationbarrier may be used, for example, to control heat flow or air flowbetween cell types during normal battery operation. In the embodimentillustrated in FIG. 6, no separation barrier is used.

In system 600, pack 601 includes at least a pair of passageways 607 and609 that allow air to flow into and out of pack 601. The flow of airthrough passageways 607 and 609 is preferably controlled by valves 608and 610, respectively. It will be appreciated that while passageways 607and 609 are shown as singular passageways, each of them may be comprisedof multiple passageways in order to provide sufficient air flow, andtherefore oxygen, for metal-air cells 603. During a thermal event,passageway 609 is closed (e.g., using valve 610), forcing the hot gasand material generated by one or more non-metal-air cells 605 undergoingthermal runaway to pass through metal-air cells 603 before beingexpelled through passageway 607. In some embodiments passageway 607 isclosed (e.g., using valve 608) during the initial stages of the thermalevent, thus delaying the escape of hot gas to the ambient atmosphere.Typically passageway 607 is opened soon after initiation of thermalrunaway, thus ensuring that the hot gas passes through metal-air cells603. Alternately, passageway 607 may be opened only a small amountduring the early stages of the event, sufficient to direct the flow ofhot gas through the metal-air cells while still limiting airflow out ofthe pack. As noted above, preferably battery pack 601 includes asecondary high pressure relief valve 611 to avoid over-pressuring pack601 once the pores of the porous metal electrodes of the metal-air cells603 become clogged.

FIG. 7 illustrates a slight modification of system 600. As shown, withinbattery pack 701, metal-air cells 603 are separated from non-metal-aircells 605 by barrier 703. Barrier 703 prevents the flow of air betweenthe two sets of cell. Accordingly, during normal operation air flowsinto the portion of battery pack 701 containing metal-air cells 603through one or more passageways 607, and then out of this portion of thebattery pack via one or more passageways 705. Typically the direction ofair flow depends upon the orientation and positioning of cells 603within the battery pack as it is important to maximize air flow duringthe discharge cycle in order to optimize battery performance.

In system 700, during a thermal runaway event a valve 707 opens up anair passageway 708 through barrier 703, thus allowing the hot gas andmaterial generated during the event to flow through metal-air cells 603.In addition to opening passageway 707, preferably the passageways thatcontrol airflow into and out of the portion of pack 701 containingmetal-air cells 603 are also adjusted, for example altering passageways705 (e.g., using valves 706) to optimize the flow of hot gas from thenon-metal-air cells through the metal-air cells. For example, inaddition to opening passageway 707 of system 700 during thermal runawayof a non-metal-air cell, preferably passageway 607 is opened andpassageways 705 are closed, thus directing the flow of hot gas andmaterial from the non-metal-air cells through the metal-air cells beforeexiting the pack.

As previously noted, the present invention may be used in a variety ofdifferent system configurations. System 800, shown in FIG. 8, utilizesseparate battery packs, i.e., metal-air battery pack 101 andconventional battery pack 103. Preferably, and as shown, a plenum 801 isused to direct the flow of air through metal-air cells 603. It should beunderstood, however, that other means may be used to direct the flow ofair through cells 603, and that plenum 801 is not a requirement of theinvention.

During normal operation, preferably non-metal-air battery pack 103 isclosed as previously noted, and air is directed into plenum 801 viapassageway 803, the flow through passageway 803 under the control ofvalve 804. After passing through the metal-air cells 603, the air leavesbattery pack 101 via one or more passageways 805. The air flow throughpassageway 805 is preferably controlled by a valve 806. Once anon-metal-air cell 605 within battery pack 103 begins to overheat andenter into a thermal runaway condition, a valve 809 opens, allowing hotgas and material generated during the event to exit pack 103 viapassageway 810 and enter duct 811. At approximately the same time, valve804 closes and a valve 813 opens, valve 813 allowing the hot gasexpelled from battery pack 103 to flow through duct 811 and into plenum801 via passageway 814. Plenum 801 directs the flow through metal-aircells 803. Exemplary pathways 815 illustrate some of the flow pathwaysthrough passageway 814 and plenum 801.

In system 800, preferably the two battery packs are in close proximityto one another, thereby allowing the length of duct 811 to be minimized.In some configurations, duct 811 may be eliminated altogether. Forexample, FIG. 9 illustrates slight modification of system 800. As shown,battery packs 101 and 103 are adjacent to one another. In thisembodiment, during a thermal event valve 901, controlling the flow ofambient (or other) air into plenum 903 via passageway 902, is closed andvalve 903 is opened, thereby allowing the hot gas generated during thethermal event within pack 103 to pass through passageway 904 into plenum905, and thus through metal-air cells 603 via exemplary pathways 907.

In the systems illustrated in FIGS. 8 and 9, if the valve 806controlling passageway 805 is closed, the hot gas and material from pack101 will flow into pack 103 until a pressure equilibrium is reachedbetween the packs. The hot gas and material will then be containedwithin the packs until the thermal event is finished and the packs cool,or until there is a failure within one of the packs (e.g., at anenclosure joint or in a duct, seal, feed-through, valve, etc.). Giventhe volume of gas generated during a typical thermal runaway event, itwill be appreciated that for most systems, maintaining a closed systemis not a viable option. Accordingly, in a typical application,passageway 805 is only temporarily sealed, if sealed at all, during theinitial stage of thermal runaway. At a predetermined pressure and/ortemperature, valve 806 is opened, thus allowing the hot gas and materialgenerated by the event and passing through the metal-air cells to exitthe system. As noted above, for many applications the temperature of thehot gas will have been sufficiently reduced to significantly lower therisk of spontaneous combustion of materials in proximity to the expelledhot gas as well as the risks to vehicle occupants, first responders andbystanders.

In addition to operation of the valve controlling flow throughpassageway 805, and as noted in the above configurations, preferablybattery pack 103 includes a secondary high pressure escape valve 817that prevents the system from becoming over-pressurized once the poreswithin the porous metal electrodes of the metal-air cells becomeclogged. Valve 817 is designed to open at a predetermined pressureand/or temperature that is less than that which would cause thegeneration of a failure point in one of the packs, ducting,feed-through, seals, etc., but at a sufficiently high pressure, ortemperature, to significantly delay the expulsion of hot gas from pack101.

The present invention may be implemented either as a mechanical systemin which the disclosed hazard mitigation system is automaticallyimplemented by action of one or more valves, or as a smart system inwhich the valves are under the control of a control system thatdetermines when to open and/or close the control valves. In the firstconfiguration, valves may be used that are designed to open gradually,or completely, based on the pressure and/or temperature. In the secondconfiguration, which is preferred, the valves controlling air flowthrough the battery packs are under the control of a system controller.Regardless of the technique used to control valve operation, it isimportant that the valve controlling the flow of hot gas out of theconventional battery pack (e.g., valve 301 in FIGS. 3-5; valve 707 inFIG. 7; valve 809 in FIG. 8; and valve 903 in FIG. 9) opens rapidly,preferably at the onset of a thermal event, thereby quickly mitigatingthe early effects of a cell undergoing thermal runaway and potentiallypreventing the initial thermal runaway event from spreading throughoutthe pack. A rapid response by the system can help contain the event,thus improving the safety to passengers, bystanders and first respondersand lowering the risk of collateral damage.

FIGS. 10-13 illustrate the embodiments shown in FIGS. 6-9, modified toinclude a system controller 1001 that (i) determines whether a valve isto be opened or closed, and (ii) controls the opening/closing of thevalves. As noted below, controller 1001 may be used to control all ofthe valves, or a subset of the valves. Controller 1001, which includes aprocessor and memory, may be a stand-alone controller or integratedwithin another vehicle control system.

FIG. 10 corresponds to FIG. 6, with the addition of controller 1001. Inthis embodiment, system controller 1001 determines and controls theoperation of valves 608 and 610. Thus, for example, if the metal-aircells 603 are in the discharge mode, controller 1001 opens valves 608and 610 to ensure sufficient oxygen reaches the cells. Controller 1001also monitors the pressure and/or temperature within pack 601 andcompares the monitored pressure and/or temperature to a presettemperature and/or pressure, the preset values being stored within thecontroller's memory. FIG. 10 includes at least one pressure sensor 1003and at least one temperature sensor 1005, although it will beappreciated that the system may monitor only pressure or onlytemperature, controlling the valves based on the monitored values. Insystem 1000, once controller 1001 determines that a thermal event isunderway, either by determining that the pressure within pack 601 isgreater than expected during normal operation or that the temperaturewithin pack 601 is greater than expected during normal operation, valve610 is closed, thereby forcing the hot gas and material generated by thethermal event to pass through metal-air cells 603 before being expelledthrough passageway 607. Assuming that the system includes a secondarypressure relief valve 611 as described above, preferably it is alsounder the control of controller 1001 as shown, although in at least oneembodiment, valve 611 is a mechanical valve that operates independentlyof controller 1001. If valve 611 is under the control of controller1001, as preferred, then controller 1001 opens valve 611 once thepressure within pack 601 exceeds a second preset value, indicating thatthe pores within the metal-air cells have become clogged from thematerial generated by the thermal event and that the pressure within thebattery pack has exceeded the second preset value. Preferably the secondpreset value is less than the failure pressure of the pack.

FIG. 11 corresponds to FIG. 7, with the inclusion of controller 1001.This system operates in a manner similar to that described previously,given the different valve arrangement. Thus, for example, during normaloperation controller 1001 keeps valve 707 closed and valves 608 and 706open to provide air flow for the metal-air cells. Once a thermal eventis detected, controller 1001 opens valve 707 and closes valves 706,thereby forcing the hot gas and material generated by the thermal eventto pass through metal-air cells 603 before being expelled throughpassageway 607.

FIG. 12 corresponds to FIG. 8, with the inclusion of controller 1001.This system operates in a manner similar to that described previously,given the different valve arrangement. During normal operationcontroller 1001 keeps valves 809 and 813 closed, and valves 804 and 806open, thus isolating the non-metal-air cells while providing air flow,and thus oxygen, to metal-air cells 603. When a thermal event isdetected, controller 1001 opens valves 809 and 813, and closes valve804, thereby forcing the hot gas and material generated by the thermalevent to pass through metal-air cells 603 before being expelled throughpassageway 805. As in the embodiments shown in FIGS. 10 and 11,preferably secondary pressure relief valve 817 is under the control ofcontroller 1001, valve 817 being opened when the air flow through themetal-air cells becomes too restrictive, causing the pressure within theconventional battery pack to increase to an undesirable level.

FIG. 13 corresponds to FIG. 9, with the inclusion of controller 1001.This system operates in a manner similar to that described previously,given the different valve arrangement. Thus, for example, during normaloperation controller 1001 keeps valve 903 closed and valves 901 and 806open. When a thermal event is detected, controller 1001 opens valve 903and closes valve 901 in order to force the thermal event effluent topass through the metal-air cells before being expelled throughpassageway 805.

It will be appreciated that the invention may be incorporated into otherconfigurations and embodiments than those shown and described above, andthe illustrated configurations and embodiments are only meant toillustrate the primary aspects of the invention. For example, themetal-air battery pack may utilize more than the number of illustratedinlets in order to achieve the desired airflow during normal metal-airbattery pack operation. To illustrate another variation of theinvention, FIG. 14 shows a modification of the embodiment shown in FIG.13. In system 1400, controller 1001 also monitors the pressure and/ortemperature within metal-air battery pack 101 using sensor 1401. In oneconfiguration, during the initial stages of a thermal event, controller1001 closes valve 806, thus further delaying the expulsion of hot gasfrom the system. Once the pressure and/or temperature within batterypack 101 exceeds a preset value, or once the pressure within packs 101and 103 equalize, controller 1001 opens valve 806. Alternately,controller 1001 may control the amount that valve 806 is opened based onthe pressure within pack 101, for example just cracking valve 806 openduring the initial stages of the thermal event, and then increasing airflow through passageway 805 as the pressure within pack 101 increasesdue to the escalation of the thermal event. The techniques illustratedin FIG. 14, i.e., monitoring conditions within the metal-air batterypack in order to further control air flow through the metal-air cells,may be used with any of the other configurations and embodiments of theinvention.

It should also be understood that the invention may utilize any means todetect the occurrence of thermal runaway and initiate the disclosedmitigation procedures, i.e., flowing thermal event effluent through themetal-air cells. While pressure and/or temperature are routinely used todetect thermal events, other means may also be used, for example,monitoring the operational condition of the individual non-metal-aircells or groups of non-metal-air cells in order to detect short circuitsor other non-standard operating conditions. Regardless of the means usedto detect a thermal event, once such an event is detected, the system ofthe invention would alter the air flow, forcing the hot gas and materialgenerated during the event to pass through the metal-air cells.

As will be understood by those familiar with the art, the presentinvention may be embodied in other specific forms without departing fromthe spirit or essential characteristics thereof. Accordingly, thedisclosures and descriptions herein are intended to be illustrative, butnot limiting, of the scope of the invention which is set forth in thefollowing claims.

What is claimed is:
 1. A hazard mitigation system, comprising: a powersource, comprising: a first battery pack comprised of a plurality ofmetal-air cells, said first battery pack further comprised of at least afirst air passageway, a second air passageway, and a third airpassageway; a second battery pack comprised of a plurality ofnon-metal-air cells, said second battery pack further comprised of a hotgas outlet; means for coupling said hot gas outlet of said secondbattery pack to said third passageway of said first battery pack; and afirst valve, said first valve controlling air flow out of said secondbattery pack and through said hot gas outlet and through said thirdpassageway and through at least a portion of said plurality of metal-aircells within said first battery pack, said first valve having at least afirst position that permits air flow and a second position that preventsair flow, wherein during normal operation of said power source saidfirst valve is in said second position, and wherein said first valve isconfigured to switch from said second position to said first positionupon the occurrence of a thermal event within said second battery pack.2. The hazard mitigation system of claim 1, wherein said first valveswitches from said second position to said first position at a presettemperature within said second battery pack, wherein said presettemperature corresponds to at least one of said plurality ofnon-metal-air cells entering into thermal runaway.
 3. The hazardmitigation system of claim 1, further comprising a system controllercoupled to said first valve and to at least one temperature sensorwithin said second battery pack, wherein said system controller switchessaid first valve from said second position to said first position when atemperature monitored by said at least one temperature sensor exceeds apreset temperature, wherein said preset temperature corresponds to atleast one of said plurality of non-metal-air cells entering into thermalrunaway.
 4. The hazard mitigation system of claim 1, wherein said firstvalve switches from said second position to said first position at apreset pressure within said second battery pack, wherein said presetpressure corresponds to at least one of said plurality of non-metal-aircells entering into thermal runaway.
 5. The hazard mitigation system ofclaim 1, further comprising a system controller coupled to said firstvalve and to at least one pressure sensor within said second batterypack, wherein said system controller switches said first valve from saidsecond position to said first position when a pressure monitored by saidat least one pressure sensor exceeds a preset pressure, wherein saidpreset pressure corresponds to at least one of said plurality ofnon-metal-air cells entering into thermal runaway.
 6. The hazardmitigation system of claim 1, further comprising a second valvecorresponding to said first air passageway of said first battery pack,said second valve having at least a first position that permits air flowand a second position that prevents air flow, and wherein said secondvalve is configured to switch to said second position upon theoccurrence of a thermal event within said second battery pack.
 7. Thehazard mitigation system of claim 6, wherein said first valve switchesfrom said second position to said first position at a preset temperaturewithin said second battery pack, wherein said second valve switches tosaid second position at said preset temperature, and wherein said presettemperature corresponds to at least one of said plurality ofnon-metal-air cells entering into thermal runaway.
 8. The hazardmitigation system of claim 6, further comprising a system controllercoupled to said first valve, said second valve, and to at least onetemperature sensor within said second battery pack, wherein said systemcontroller switches said first valve from said second position to saidfirst position and switches said second valve to said second positionwhen a temperature monitored by said at least one temperature sensorexceeds a preset temperature, and wherein said preset temperaturecorresponds to at least one of said plurality of non-metal-air cellsentering into thermal runaway.
 9. The hazard mitigation system of claim6, wherein said first valve switches from said second position to saidfirst position at a preset pressure within said second battery pack,wherein said second valve switches to said second position at saidpreset pressure, and wherein said preset pressure corresponds to atleast one of said plurality of non-metal-air cells entering into thermalrunaway.
 10. The hazard mitigation system of claim 6, further comprisinga system controller coupled to said first valve, said second valve, andto at least one pressure sensor within said second battery pack, whereinsaid system controller switches said first valve from said secondposition to said first position and switches said second valve to saidsecond position when a pressure monitored by said at least one pressuresensor exceeds a preset pressure, and wherein said preset pressurecorresponds to at least one of said plurality of non-metal-air cellsentering into thermal runaway.
 11. The hazard mitigation system of claim1, further comprising: a second valve corresponding to said first airpassageway of said first battery pack, said second valve having at leasta first position that permits air flow and a second position thatprevents air flow, wherein said second valve is configured to switch tosaid second position upon the occurrence of a thermal event within saidsecond battery pack; a third valve corresponding to said second airpassageway of said first battery pack, said third valve having at leasta first position that permits air flow and a second position thatprevents air flow; at least a first temperature sensor within said firstbattery pack and at least a second temperature sensor within said secondbattery pack; and a system controller coupled to said first valve, saidsecond valve, said third valve, said first temperature sensor and saidsecond temperature sensor, wherein said system controller switches saidfirst valve from said second position to said first position andswitches said second valve to said second position when a second batterypack temperature monitored by said second temperature sensor exceeds afirst preset temperature, wherein said first preset temperaturecorresponds to at least one of said plurality of non-metal-air cellsentering into thermal runaway, wherein said system controller maintainssaid third valve in said second position when said second battery packtemperature monitored by said second temperature sensor exceeds saidfirst preset temperature and said first battery pack temperaturemonitored by said first temperature sensor is less than a second presettemperature, and wherein said system controller maintains said thirdvalve in said first position when said second battery pack temperaturemonitored by said second temperature sensor exceeds said first presettemperature and said first battery pack temperature monitored by saidfirst temperature sensor exceeds said second preset temperature.
 12. Thehazard mitigation system of claim 1, further comprising: a second valvecorresponding to said first air passageway of said first battery pack,said second valve having at least a first position that permits air flowand a second position that prevents air flow, wherein said second valveis configured to switch to said second position upon the occurrence of athermal event within said second battery pack; a third valvecorresponding to said second air passageway of said first battery pack,said third valve having at least a first position that permits air flowand a second position that prevents air flow; at least a first pressuresensor within said first battery pack and at least a second pressuresensor within said second battery pack; and a system controller coupledto said first valve, said second valve, said third valve, said firstpressure sensor and said second pressure sensor, wherein said systemcontroller switches said first valve from said second position to saidfirst position and switches said second valve to said second positionwhen a second battery pack pressure monitored by said second pressuresensor exceeds a first preset pressure, wherein said first presetpressure corresponds to at least one of said plurality of non-metal-aircells entering into thermal runaway, wherein said system controllermaintains said third valve in said second position when said secondbattery pack pressure monitored by said second pressure sensor exceedssaid first preset pressure and said first battery pack pressuremonitored by said first pressure sensor is less than a second presetpressure, and wherein said system controller maintains said third valvein said first position when said second battery pack pressure monitoredby said second pressure sensor exceeds said first preset pressure andsaid first battery pack pressure monitored by said first pressure sensorexceeds said second preset pressure.
 13. The hazard mitigation system ofclaim 1, further comprising: a second valve corresponding to said firstair passageway of said first battery pack, said second valve having atleast a first position that permits air flow and a second position thatprevents air flow, wherein said second valve is configured to switch tosaid second position upon the occurrence of a thermal event within saidsecond battery pack; a third valve corresponding to said second airpassageway of said first battery pack, said third valve having at leasta first position that permits air flow and a second position thatprevents air flow; at least a first temperature sensor within said firstbattery pack and at least a first pressure sensor within said secondbattery pack; and a system controller coupled to said first valve, saidsecond valve, said third valve, said first temperature sensor and saidfirst pressure sensor, wherein said system controller switches saidfirst valve from said second position to said first position andswitches said second valve to said second position when a second batterypack pressure monitored by said first pressure sensor exceeds a firstpreset pressure, wherein said first preset pressure corresponds to atleast one of said plurality of non-metal-air cells entering into thermalrunaway, wherein said system controller maintains said third valve insaid second position when said second battery pack pressure monitored bysaid first pressure sensor exceeds said first preset pressure and saidfirst battery pack temperature monitored by said first temperaturesensor is less than a first preset temperature, and wherein said systemcontroller maintains said third valve in said first position when saidsecond battery pack pressure monitored by said first pressure sensorexceeds said first preset pressure and said first battery packtemperature monitored by said first temperature sensor exceeds saidfirst preset temperature.
 14. The hazard mitigation system of claim 1,further comprising: a second valve corresponding to said first airpassageway of said first battery pack, said second valve having at leasta first position that permits air flow and a second position thatprevents air flow, wherein said second valve is configured to switch tosaid second position upon the occurrence of a thermal event within saidsecond battery pack; a third valve corresponding to said second airpassageway of said first battery pack, said third valve having at leasta first position that permits air flow and a second position thatprevents air flow; at least a first pressure sensor within said firstbattery pack and at least a first temperature sensor within said secondbattery pack; and a system controller coupled to said first valve, saidsecond valve, said third valve, said first pressure sensor and saidfirst temperature sensor, wherein said system controller switches saidfirst valve from said second position to said first position andswitches said second valve to said second position when a second batterypack temperature monitored by said first temperature sensor exceeds afirst preset temperature, wherein said first preset temperaturecorresponds to at least one of said plurality of non-metal-air cellsentering into thermal runaway, wherein said system controller maintainssaid third valve in said second position when said second battery packtemperature monitored by said first temperature sensor exceeds saidfirst preset temperature and said first battery pack pressure monitoredby said first pressure sensor is less than a first preset pressure, andwherein said system controller maintains said third valve in said firstposition when said second battery pack temperature monitored by saidfirst temperature sensor exceeds said first preset temperature and saidfirst battery pack pressure monitored by said first pressure sensorexceeds said first preset pressure.
 15. The hazard mitigation system ofclaim 1, wherein said means for coupling said hot gas outlet of saidsecond battery pack to said third passageway of said first battery packcomprises a duct, said hazard mitigation system further comprising: asecond valve corresponding to said first air passageway of said firstbattery pack, said second valve having at least a first position thatpermits air flow and a second position that prevents air flow, andwherein said second valve is configured to switch to said secondposition upon the occurrence of a thermal event within said secondbattery pack; and a third valve corresponding to said third airpassageway of said first battery pack, said third valve controlling airflow from said hot gas outlet and through said third passageway andthrough at least a portion of said plurality of metal-air cells withinsaid first battery pack, said third valve having at least a firstposition that permits air flow and a second position that prevents airflow, wherein during normal operation of said power source said thirdvalve is in said second position, and wherein said third valve isconfigured to switch from said second position to said first positionupon the occurrence of said thermal event within said second batterypack.
 16. The hazard mitigation system of claim 15, wherein said firstvalve switches from said second position to said first position at apreset temperature within said second battery pack, wherein said thirdvalve switches from said second position to said first position at saidpreset temperature, wherein said second valve switches to said secondposition at said preset temperature, and wherein said preset temperaturecorresponds to at least one of said plurality of non-metal-air cellsentering into thermal runaway.
 17. The hazard mitigation system of claim15, further comprising a system controller coupled to said first valve,said second valve, said third valve, and to at least one temperaturesensor within said second battery pack, wherein said system controllerswitches said first valve from said second position to said firstposition and switches said third valve from said second position to saidfirst position and switches said second valve to said second positionwhen a temperature monitored by said at least one temperature sensorexceeds a preset temperature, and wherein said preset temperaturecorresponds to at least one of said plurality of non-metal-air cellsentering into thermal runaway.
 18. The hazard mitigation system of claim15, wherein said first valve switches from said second position to saidfirst position at a preset pressure within said second battery pack,wherein said third valve switches from said second position to saidfirst position at said preset pressure, wherein said second valveswitches to said second position at said preset pressure, and whereinsaid preset pressure corresponds to at least one of said plurality ofnon-metal-air cells entering into thermal runaway.
 19. The hazardmitigation system of claim 15, further comprising a system controllercoupled to said first valve, said second valve, said third valve, and toat least one pressure sensor within said second battery pack, whereinsaid system controller switches said first valve from said secondposition to said first position and switches said third valve from saidsecond position to said first position and switches said second valve tosaid second position when a pressure monitored by said at least onepressure sensor exceeds a preset pressure, and wherein said presetpressure corresponds to at least one of said plurality of non-metal-aircells entering into thermal runaway.
 20. The hazard mitigation system ofclaim 1, said first battery pack further comprising a plenum, saidplenum directing air flow from said first and third air passagewaysthrough said plurality of metal-air cells.
 21. The hazard mitigationsystem of claim 1, said second battery pack further comprising a highpressure relief valve.
 22. A method of mitigating the effects of athermal event within a non-metal-air battery pack, the method comprisingthe steps of: coupling a hot gas outlet corresponding to saidnon-metal-air battery pack to an air inlet of a metal-air battery packupon the occurrence of said thermal event within said non-metal-airbattery pack; and directing air flow from said hot gas outlet of saidnon-metal-air battery pack through said air inlet of said metal-airbattery pack and through a plurality of metal-air cells within saidmetal-air battery pack upon the occurrence of said thermal event withinsaid non-metal-air battery pack.
 23. The method of claim 22, furthercomprising the step of opening a valve that controls said air flow fromsaid hot gas outlet of said non-metal-air battery pack, wherein saidstep of opening said valve is performed when a temperature within saidnon-metal-air battery pack exceeds a preset temperature, wherein saidpreset temperature corresponds to at least one of a plurality ofnon-metal-air cells within said non-metal-air battery pack entering intothermal runaway.
 24. The method of claim 22, further comprising the stepof opening a valve that controls said air flow from said hot gas outletof said non-metal-air battery pack, wherein said step of opening saidvalve is performed when a pressure within said non-metal-air batterypack exceeds a preset pressure, wherein said preset pressure correspondsto at least one of a plurality of non-metal-air cells within saidnon-metal-air battery pack entering into thermal runaway.
 25. The methodof claim 22, further comprising the steps of: monitoring a temperaturewithin said non-metal-air battery pack; comparing said temperaturewithin said non-metal-air battery pack to a preset temperature, saidpreset temperature corresponding to at least one of a plurality ofnon-metal-air cells within said non-metal-air battery pack entering intothermal runaway; and opening a valve that controls said air flow fromsaid hot gas outlet of said non-metal-air battery pack when saidtemperature within said non-metal-air battery pack exceeds said presettemperature.
 26. The method of claim 22, further comprising the stepsof: monitoring a pressure within said non-metal-air battery pack;comparing said pressure within said non-metal-air battery pack to apreset pressure, said preset pressure corresponding to at least one of aplurality of non-metal-air cells within said non-metal-air battery packentering into thermal runaway; and opening a valve that controls saidair flow from said hot gas outlet of said non-metal-air battery packwhen said pressure within said non-metal-air battery pack exceeds saidpreset pressure.
 27. The method of claim 22, further comprising thesteps of: opening a first valve that controls said air flow from saidhot gas outlet of said non-metal-air battery pack, wherein said step ofopening said first valve is performed when a non-metal-air battery packtemperature within said non-metal-air battery pack exceeds a firstpreset temperature, wherein said first preset temperature corresponds toat least one of a plurality of non-metal-air cells within saidnon-metal-air battery pack entering into thermal runaway; and closing asecond valve that controls air flow from a primary air source throughsaid air inlet of said metal-air battery pack and through said pluralityof metal-air cells within said metal-air battery pack, wherein saidprimary air source is different from said hot gas outlet, and whereinsaid step of closing said second valve is performed when saidnon-metal-air battery pack temperature exceeds said first presettemperature.
 28. The method of claim 27, further comprising the stepsof: closing a third valve that controls air flow out of said metal-airbattery pack and to an ambient environment, wherein said step of closingsaid third valve is performed when said non-metal-air battery packtemperature exceeds said first preset temperature; and opening saidthird valve that controls air flow out of said metal-air battery packand to said ambient environment, wherein said step of opening said thirdvalve is performed when a metal-air battery pack temperature within saidmetal-air battery pack exceeds a second preset temperature, and whereinsaid step of opening said third valve occurs after said step of closingsaid third valve.
 29. The method of claim 27, further comprising thesteps of: closing a third valve that controls air flow out of saidmetal-air battery pack and to an ambient environment, wherein said stepof closing said third valve is performed when said non-metal-air batterypack temperature exceeds said first preset temperature; and opening saidthird valve that controls air flow out of said metal-air battery packand to said ambient environment, wherein said step of opening said thirdvalve is performed when a metal-air battery pack pressure within saidmetal-air battery pack exceeds a preset pressure, and wherein said stepof opening said third valve occurs after said step of closing said thirdvalve.
 30. The method of claim 22, further comprising the steps of:opening a first valve that controls said air flow from said hot gasoutlet of said non-metal-air battery pack, wherein said step of openingsaid first valve is performed when a non-metal-air battery pack pressurewithin said non-metal-air battery pack exceeds a first preset pressure,wherein said first preset pressure corresponds to at least one of aplurality of non-metal-air cells within said non-metal-air battery packentering into thermal runaway; and closing a second valve that controlsair flow from a primary air source through said air inlet of saidmetal-air battery pack and through said plurality of metal-air cellswithin said metal-air battery pack, wherein said primary air source isdifferent from said hot gas outlet, and wherein said step of closingsaid second valve is performed when said non-metal-air battery packpressure exceeds said first preset pressure.
 31. The method of claim 30,further comprising the steps of: closing a third valve that controls airflow out of said metal-air battery pack and to an ambient environment,wherein said step of closing said third valve is performed when saidnon-metal-air battery pack pressure exceeds said first preset pressure;and opening said third valve that controls air flow out of saidmetal-air battery pack and to said ambient environment, wherein saidstep of opening said third valve is performed when a metal-air batterypack pressure within said metal-air battery pack exceeds a second presetpressure, and wherein said step of opening said third valve occurs aftersaid step of closing said third valve.
 32. The method of claim 30,further comprising the steps of: closing a third valve that controls airflow out of said metal-air battery pack and to an ambient environment,wherein said step of closing said third valve is performed when saidnon-metal-air battery pack pressure exceeds said first preset pressure;and opening said third valve that controls air flow out of saidmetal-air battery pack and to said ambient environment, wherein saidstep of opening said third valve is performed when a metal-air batterypack temperature within said metal-air battery pack exceeds a presettemperature, and wherein said step of opening said third valve occursafter said step of closing said third valve.